The New Horizons spacecraft has caught a glimpse of the massive, glowing wall of hydrogen that surrounds the solar system.
This "wall" marks the edge of the sun's neighborhood, the point where rest of the galaxy and the universe begins.
"We're seeing the threshold between being in the solar neighborhood and being in the galaxy," Leslie Young of the Southwest Research Institute explains in a statement to Science News.
Eerie Glow Signals The Neighborhood Boundary
The powerful solar wind from the sun flows outward continuously, passing far beyond even Pluto's region. However, Live Science explains that at a certain point, the sun's jet streams inevitably lose energy and become unable to push the mysterious bits of cosmic dust any further.
It is at this point that a visible "glow" appears, the wall where the solar wind stops extending out and interstellar matter that is too small to penetrate the jets accumulates.
Two Voyager spacecraft saw signs of light emanating from this boundary in 1992, but until now, no other probe has been in a position to double-check.
In a paper published in the journal Geophysical Research Letters on Tuesday, Aug. 7, the New Horizons team reveals that the spacecraft was able to spot ultraviolet light that supports the existence of a "hydrogen wall" signaling the boundary of the solar system.
Randy Gladstone, an astronomer at the Southwest Research Institute in San Antonio, and his colleagues reported that the New Horizons spacecraft scanned the ultraviolet sky seven times in its journey outward through the past decade. The findings were consistent with the Voyager records — that more ultraviolet light was detected farther from the sun than expected in the absence of a wall.
More Studies Needed On The Wall
Of course, the team acknowledges that similar findings from the Voyager spacecraft and the New Horizon probe are not enough evidence to definitively confirm the presence of a hydrogen wall. After all, it is entirely possible that the ultraviolet light comes from an unknown source.
Still, the second account of the boundary is a big step forward in learning about the edge of the solar system.
David McComas, an astronomer from Princeton University who was not involved in the study, explains that if the collected data could distinguish the hydrogen wall, scientists could eventually figure out the shape and variability of the galaxy's boundary.
In the coming years, more data are expected to come in about this mysterious wall. New Horizons will be looking for the boundary about twice a year for the rest of the mission.